Semiconductor device and method for manufacturing the same

Abstract

A method for manufacturing a thin film transistor (TFT) through a process including back exposure, in which oxide semiconductor is used for a channel layer; using an electrode over a substrate as a mask, negative resist is exposed to light from the back of the substrate; the negative resist except its exposed part is removed; and an electrode is shaped by etching a conductive film using the exposed part as an etching mask.

1. A method for manufacturing a semiconductor device, comprising the steps of:
 forming, over a substrate, a source electrode and a drain electrode from a metal film and 
 a channel layer from oxide semiconductor; 
 forming a gate insulating film over the source electrode, the drain electrode, and the channel layer; 
 forming a conductive film over the gate insulating film 
 coating the conductive film with negative resist; 
 exposing the negative resist to light from a back of the substrate using the source electrode and the drain electrode as a mask; 
 removing the negative resist except for an exposed part of the negative resist; 
 forming a gate electrode by etching the conductive film using the exposed part as an etching mask; 
 forming a first interconnect from the metal film on the substrate together with the source electrode and the drain electrode; 
 exposing the negative resist to light from the back of the substrate using, as a mask, the first interconnect as well as the source electrode and the drain electrode; 
 exposing part of the negative resist just above the first interconnect to light from a front side of the substrate through a photo mask; 
 removing the negative resist except exposed part of the negative resist; and 
 forming a second interconnect together with the age electrode by etching the conductive film using the exposed part as an etching mask. 
 
     
     
       2. The method for manufacturing a semiconductor device according to  claim 1 , further comprising:
 forming a third interconnect in an area of division of the second interconnect just above the first interconnect to connect the area. 
 
     
     
       3. The method for manufacturing a semiconductor device according to  claim 1 , wherein i rays of a mercury lamp are used as a light source for the back exposure. 
     
     
       4. The method for manufacturing a semiconductor device according to  claim 1 , wherein the substrate is a plastic film. 
     
     
       5. The method for manufacturing a semiconductor device according to  claim 1 , wherein the channel layer is made of Zn—O, In—O, Ga—O, Sn—O, In—Ga—Zn—O, Zn—Sn—O, In—Sn—O, In—Zn—O, Ga—Zn—O or In—Ga—O. 
     
     
       6. The method for manufacturing a semiconductor device according to  claim 1 , wherein the gate insulating film is made of Si—O, Al—O or Si—N. 
     
     
       7. The method for manufacturing a semiconductor device according to  claim 1 , wherein the conductive film is made of In—Sn—O, Al—Zn—O, or Sn—O. 
     
     
       8. The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein the substrate, the channel layer, the gate insulating film, and the conductive film are transparent; and 
 wherein the metal film is opaque. 
 
     
     
       9. A method for manufacturing a semiconductor device, comprising the steps of:
 forming a gate electrode from a metal film over a substrate; 
 forming a gate insulating film over the gate electrode and the substrate; 
 forming a channel layer from oxide semiconductor over the gate insulating film; 
 forming a conductive film over the channel layer; 
 coating the conductive film with negative resist; 
 exposing the negative resist to light from a back of the substrate using the gate electrode as a mask; 
 removing the negative resist except for an exposed part of the negative resist; and 
 forming a source electrode and a drain electrode by etching the conductive film using the exposed part as an etching mask; 
 forming a first interconnect from the metal film on the substrate together with the gate electrode; 
 exposing the negative resist to light from the back of the substrate using, as a mask, the first interconnect as well as the gate electrode; 
 exposing part of the negative resist just above the first interconnect to light from a front side of the substrate through a photo mask; 
 removing the negative resist except exposed part of the negative resist; and 
 forming a second interconnect together with the source electrode and the drain electrode by etching the conductive film using the exposed part as an etching mask. 
 
     
     
       10. The method for manufacturing a semiconductor device according to  claim 9 , further comprising:
 forming a third interconnect in an area of division of the second interconnect just above the first interconnect to connect the area. 
 
     
     
       11. The method for manufacturing a semiconductor device according to  claim 9 , wherein i rays of a mercury lamp are used as a light source for the back exposure. 
     
     
       12. The method for manufacturing a semiconductor device according to  claim 9 , wherein the substrate is a plastic film. 
     
     
       13. The method for manufacturing a semiconductor device according to  claim 9 , wherein the channel layer is made of Zn—O, In—O, Ga—O, Sn—O, In—Ga—Zn—O, Zn—Sn—O, In—Sn—O, In—Zn—O, Ga—Zn—O or In—Ga—O. 
     
     
       14. The method for manufacturing a semiconductor device according to  claim 9 , wherein the gate insulating film is made of Si—O, Al—O or Si—N. 
     
     
       15. The method for manufacturing a semiconductor device according to  claim 9 , wherein the conductive film is made of In—Sn—O, Al—Zn—O, or Sn—O. 
     
     
       16. The method for manufacturing a semiconductor device according to  claim 9 ,
 wherein the substrate, the channel layer, the gate insulating film, and the conductive film are transparent; and 
 wherein the metal film is opaque. 
 
     
     
       17. A semiconductor device manufactured by:
 forming, over a substrate, a source electrode and a drain electrode from a metal film and a channel layer from oxide semiconductor; 
 forming a gate insulating film over the source electrode, the drain electrode, and the channel layer; 
 forming a conductive film over the gate insulating film; 
 coating the conductive film with negative resist; 
 exposing the negative resist to light from a back of the substrate using the source electrode and the drain electrode as a mask; 
 removing the negative resist except for an exposed part of the negative resist; 
 forming a gate electrode by etching the conductive film using the exposed part as an etching mask; 
 forming a first interconnect from the metal film on the substrate together with the source electrode and the drain electrode; 
 exposing the negative resist to light from the back of the substrate using, as a mask, the first interconnect as well as the source electrode and the drain electrode; 
 exposing part of the negative resist just above the first interconnect to light from a front side of the substrate through a photo mask; 
 removing the negative resist except exposed part of the negative resist; and 
 forming a second interconnect together with the gate electrode by etching the conductive film using the exposed part as an etching mask.